Wellbore integrity is almost always a consideration when conveying a casing or liner-while-drilling downhole. Wellbore integrity may be affected by reservoir depletion, complex drilling trajectory, tectonics, fault formation, or reactive formations.
In a weak geological formation, the drill bit may be combined with the casing or liner during the drilling operation. Thus, a wellbore with weak walls is lined while the wellbore is drilled. However, this may present issues with cementing the casing or liner in place due to weak formations not being able to withstand the heavier cement column, getting into a loss of cement circulation and jeopardizing the cement and borehole integrity.